Multiple Modes of Group vs Group Space PvP - Looks like there's several objective maps, and modes of play. (which you can solo/group queue for)

Tiered advancement to unlock different Space combat upgrade items to use in your new fighter/bomber ship's loadout. Notes: This is not with your class ship, and once you've unlocked all the upgrades it appears everyone will be on the same gear-level, and it will be a more skill/build-based PvP system.

Ship-only talent trees/abilities - Boy there's a ton of them, check them out in the post linked above.

Ship/Fleet XP - It looks like the SSSP will bring it's own advancement system. The Fleet XP is very interesting and I'll be watching it closely to see what exactly it is.

Eight New Space Companions (4 per Faction) - Looks like these will be crew on your new Space fighters. They seem to have individual traits and skills. Though each one of your Class's current companions will be able to assist you.

With this amount of content it's likely to be some mini-expansion like the last one, will be interesting to see how it will all work.